Environmental Engineering Reference
In-Depth Information
restricted geographically. Individuals as well as organizations can produce
biofuels, which, unlike oil, can generate income for thousands of farmers
- as opposed to just governments and a few oil companies.
Good crop, bad crop
But biofuels are a long way from unproblematic. There are good and bad
biofuels, depending on the type of plant or crop, how it is grown and
processed, and where it is grown. The whole point about biofuels is that
they ought to be a way of cutting down on fossil fuels. Any saving will
be undermined if a lot of fossil fuel has gone into the use of fertilizers,
tractors and machinery to cultivate and manufacture the biofuel in ques-
tion. The analysis of the full life-cycle of biofuels - calculating how much
fossil fuels goes into the growing and making of biofuels - is known as a
“well-to-wheels” analysis. The terminology deliberately references that of
the oil industry in order to remind us that, despite the fact that biofuels
do not come out of wells like oil, the two oils are comparable.
In terms of a well-to-wheels analysis and its carbon footprint, one of
the worst biofuels is ethanol made from maize, as grown in large amounts
in the US Mid-West. The maize requires considerable cultivation and
does not convert very easily to the sugar needed for it to ferment into the
alcohol required for ethanol. By contrast, one of the best biofuels in terms
of greenhouse-gas savings is commonly held to be the ethanol that Brazil
makes from its sugar cane. It requires relatively little cultivation and is, of
course, already a sugar.
But changes in land use are also an issue with biofuels. For there are
some types of land - wetlands, grasslands, forests and above all tropi-
cal forests - which store enormous amounts of carbon in their soil. The
conversion of these types of carbon-rich soil to biofuel cultivation might
release such large amounts of carbon that no biofuel “saving” could ever
make up the carbon loss from the original land-use change - or at best
only make up the loss over a period of many years.
This issue has raised doubts about how good a biofuel Brazilian ethanol
actually is. Brazil insists that it grows its sugar cane far from the Amazon
rainforest region. However, critics complain that expansion of sugarcane
growing in the south pushes other activities, such as cattle-rearing, further
north and adds pressure to clear the Amazon basin for cattle ranches, thus
encouraging the cutting-down of jungle and forests that absorb carbon.
 
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